1. Field of the Invention
The present invention relates to a lubricant supply device for supplying lubricant to a screw shaft of a rolling-member screw apparatus such as a ball screw.
2. Description of the Related Art
A rolling-member screw apparatus such as a linear motion rolling guide apparatus and a ball screw apparatus is known as a linear motion apparatus in which a sliding member can move relative to a track shaft through rolling members such as balls that are disposed between them.
The linear motion rolling guide apparatus can guide a movable member such as a table on a stationary member such as a bed or a saddle. The linear motion rolling guide apparatus comprises a guide rail, a movable block and a plurality of balls. The guide rail is mounted on the stationary member and has ball running grooves formed thereon, which extend in the longitudinal direction of the guide rail so as to serve as rolling-member running surfaces. The movable block has ball circulation passages formed therein, which include loaded ball running grooves serving as loaded rolling-member running surfaces corresponding to the ball running grooves of the guide rail. The movable block is fitted to the guide rail so as to be capable of making a relative motion of the former to the latter. The balls are received in the ball circulation passages in the form of trains so as to serve as the rolling members that can be circulated along with the relative motion of the movable block to the guide rail. A linear motion of the movable block supporting the movable member can be made along the guide rail along with the endless circulation of the balls.
The applicant has proposed a lubricant supply device for lubricating the guide rail of the above-described linear motion rolling guide apparatus in Japanese Patent Application No. H9-305,861. The lubricant supply device comprises a casing, an application member, an absorbent body and an oil supply adjusting plate. The casing is mounted on a sliding member. The application member is received in the casing so as to come into contact with the guide rail to apply lubricant on the guide rail. The absorbent body is received together with the application member in the casing so as to supply the lubricant to the application member. The oil supply adjusting plate locates between the absorbent body and the application member so as to supply the absorbent body to the application member.
When the sliding member moves on the guide rail, the lubricant is applied from the application member to the guide rail. When an amount of lubricant absorbed by the application member is gradually decreased, the lubricant absorbed by the absorbent body is supplied through the oil supply adjusting plate to the application member by capillary action. Accordingly, a prescribed amount of lubricant is always absorbed by the application member, thus making it possible to stably supply a prescribed amount of lubricant to be applied on the guide rail from the application member.
The rolling-member screw apparatus such as a ball screw falls under the category of the linear motion apparatus, like the above-described linear motion rolling guide apparatus. However, the rolling-member screw apparatus has specific structures that the track shaft is formed into a screw shaft provided with a rolling-member running groove having a spiral shape, the sliding member is formed into a nut member, which engages with the screw shaft and has on its inner peripheral surface a rolling-member running groove having a spiral shape, corresponds to the rolling-member running groove of the screw shaft, and rolling members such as balls run in the spiral rolling-member running groove along with the relative rotation of the screw shaft to the nut member so that the relative linear motion of the nut member to the screw shaft can be made.
There has conventionally been a demand for development of the lubricant supply device, which is the most suitable for the rolling-member screw apparatus having the above-mentioned specific structures. However, such a lubricant supply device has not as yet been developed.
An object of the present invention is therefore to provide a lubricant supply device, which is suitable for the rolling-member screw apparatus having the specific structures.
In order to attain the aforementioned object, a lubricant supply device of the present invention, which is to be fitted to a nut member engaging with a screw shaft through rolling members to supply lubricant to said screw shaft along with a relative rotational motion of said nut member to said screw shaft and comprises:
an application member for applying the lubricant on said screw shaft, said application member having at least one tongue portion, which is capable of coming into contact with at least one of rolling-member running surface of said screw shaft, a number of said at least one tongue portion being identical with or larger than a number of said rolling-member running surface;
a lubricant storage member for supplying the lubricant to said application member; and
a control device for controlling an amount of the lubricant supplied from said lubricant storage member to said application member.
According to the first device of the present invention described above, the relative rotation of the screw shaft to the nut member is made so that the lubricant is applied from the tongue portion of the application member on the surface of the rolling-member running surface of the screw shaft. The control device controls an amount of lubricant supplied from the lubricant storage member to the application member. Consequently, there is no serious change in an amount of lubricant supplied from the lubricant storage member to the application member even after a lapse of time so that a prescribed amount of lubricant can always be applied from the application member on the screw shaft. It is therefore possible to apply a minimum amount of lubricant on the screw shaft for a long period of time.
The tongue portion of the first device of the present invention, which is mounted on the nut member, can move along the spiral rolling-member-running surface along with the relative rotation of the nut member to the screw shaft. The number of the tongue portion is identical with or larger than the number of the rolling-member running surface. Accordingly, the spiral rolling-member running surface of the screw shaft can be lubricated over its entire length, irrespective of the number of the rolling-member running surface.
As the application member, there may be used material, which can smoothly apply the lubricant absorbed therein on the screw shaft, for example, oil absorbent material, which is formed of fiber-entangled body such as felt, or of sintered resin. The oil absorbent material preferably has a lower porosity than that of the other absorbent body described below, which serves as the lubricant storage member.
With respect to the lubricant storage member, any structural component, which can preserve in its inside a large amount of lubricant supplied to the application member, may suffice. As the lubricant storage member, there may be used for example either a tank having in its inside a storage chamber for receiving the lubricant, or oil absorbent material including fiber-entangled body such as felt, sintered resin or sponge by which the lubricant is actually absorbed. The oil absorbent material preferably has a higher porosity than that of the absorbent body described above, which serves as the application member.
With respect to the control device, any structural component, which can control an amount of lubricant supplied from the lubricant storage member to the application member, may suffice. As the control device, there may be used for example oil absorbent material, which is formed of fiber-entangled body such as felt, or of sintered resin. The oil absorbent material preferably has a porosity, which is middle between the high porosity of the oil absorbent material for the application member and the low porosity of the oil absorbent material for the lubricant storage member. As the control device, there may be used an oil supply adjusting plate, which can be obtained by forming supply holes through which the lubricant can passes, on a thin plate separating the lubricant storage member and the application member from each other.
There may be adopted a structure that a plurality of tongue portions are provided as said at least one tongue portion, said plurality of tongue portions locating along a single straight line, which is in parallel with a central axial line of said screw shaft. According to such a structure, it is possible to collect the lubricant supplied from the lubricant storage member in the single place, irrespective of the number of the rolling member running surface, so as to apply effectively the lubricant on the rolling-member running surface. When the rolling-member screw apparatus especially has the stationary nut member, the arrangement of the tongue portions in the lower position of the lubricant storage member causes the lubricant to gather in the single lower place under the gravity of the lubricant, thus providing more effective results.
In order to attain the above-mentioned object, the second lubricant supply device of the present invention, which is to be fitted to a nut member engaging with a screw shaft through rolling members to supply lubricant to said screw shaft along with a relative rotational motion of said nut member to said screw shaft and comprises:
an application member for applying the lubricant on said screw shaft, said application member having at least one tongue portion, which is capable of coming into contact with at least one of rolling-member running surface of said screw shaft, said at least one tongue portion locating on a single straight line, which is in parallel with a central axial line of said screw shaft;
a lubricant storage member for supplying the lubricant to said application member; and
a control device for controlling an amount of the lubricant supplied from said lubricant storage member to said application member.
According to the second device described above of the present invention, the relative rotation of the screw shaft to the nut member is made so that the lubricant is applied from the tongue portion of the application member on the surface of the rolling-member running surface of the screw shaft. Since the tongue portion locates on the single straight line, which is in parallel with the central axial line of the screw shaft, it is possible to collect the lubricant supplied from the lubricant storage member in the single place corresponding to the above-mentioned single straight line so as to apply effectively the lubricant on the rolling-member running surface. When the rolling-member screw apparatus especially has the stationary nut member, the arrangement of the tongue portions in the lower position of the lubricant storage member causes the lubricant to gather in the single lower place, thus providing more effective results.
In the second device of the present invention, the number of said at least one tongue portion may be identical with or larger than the number of said at least one rolling-member running surface, and a plurality of tongue portions may be provided as said at least one tongue portion, said plurality of tongue portions locating along a single straight line, which is in parallel with a central axial line of said screw shaft. According to the second device of the present invention, the spiral rolling-member running surface of the screw shaft can be lubricated over its entire length, irrespective of the number of the rolling-member running surface, due to the feature that the number of the tongue portion may be identical with or larger than the number of one rolling-member running surface.
In the first and second devices of the present invention, there may be adopted a structure that said lubricant storage member is formed into a tubular shape so that said screw shaft can be inserted in said lubricant storage member without causing restriction of the motion of said screw shaft; said lubricant storage member has a slit, which is separated from an inside of said lubricant storage member, said slit opening toward said screw shaft and extending along a single straight line, which is in parallel with a central axial line of said screw shaft; and said application member is fitted into said slit.
According to such a structure, the application member is fitted into the slit formed in the lubricant storage member, and it is possible to collect the lubricant received in the lubricant storage member in the single place so as to supply effectively the lubricant to the application member. The device itself can be manufactured in a small size in accordance with the size of the nut member. The lubricant storage member has a relatively large capacity by which a large amount of lubricant can be received in it.
In the first and second devices of the present invention, there may be adopted a structure that the inside of the lubricant storage member communicates with said slit at an end thereof in a longitudinal direction; said application member is formed of oil absorbent material, which can absorb the lubricant to preserve the same, into a plate-shape, said application member being fitted into said slit so as not to come into contact with the inside of said lubricant storage member; said control device comprises ajoint member, which is formed of the oil absorbent material to absorb the lubricant to carry the same, said joint member comprising a main body, which comes into contact with said application member at said one end of said slit, but does not come into contact with the inside of said lubricant storage member, and elongated portions, which extend from said main body to reach the inside of said lubricant storage member.
According to such a structure, the lubricant absorbed by the application member is applied on the surface of the rolling-member running surface of the screw shaft, while the lubricant preserved in the lubricant storage member is supplied to the application member through the elongated portions and the main body of the joint member.
The joint member is fitted into the slit formed in the lubricant storage member, and it is possible to collect the lubricant received in the lubricant storage member in the single place so as to supply effectively the lubricant to the joint member. The application member, which is formed into a plate-shape, and the main body of the joint member are fitted into the slit, which is formed in the lubricant storage member so as to open at its one end, so as to make the maximum use of the limited space. As a result, it is possible to manufacture the lubricant supply device in a smaller size.
The optimum determination of the shapes of the elongated portions and the main body of the joint member, a contact area of the elongated portions with the inside of the lubricant storage member and the contact area of the main body with the application member makes it possible to supply the lubricant from the lubricant storage member to the application member in a properly controlled manner.
In the first and second devices of the present invention, there may be adopted a structure that said lubricant storage member has a occlusion member received therein, which is formed of the oil absorbent material so as to absorb the lubricant to preserve the same; and porosities of the oil absorbent materials of said occlusion member, said joint member and said application member are determined to be larger in this order.
According to such a structure, it is possible to preserve an amount of lubricant, which is required to be applied, in the application member and impart strength, which is sufficient to bear the contact slide with the rolling-member running surface, to the application member. Use of the oil absorbent material having a high porosity as the occlusion member makes it possible to ensure the sufficient amount of lubricant preserved therein. When the fiber-entangle body, which can cause capillary action, is used as material for forming the occlusion member, the joint member and the application member, sucking force caused by the capillary action becomes larger in this order. Accordingly, no congestion of the lubricant in the passage therefor occurs, thus providing smooth supply of the lubricant.